<q>FractionalOffset</q>.<b>fromOffsetAndRect</b>(
	<q>Offset</q>(<em>20.0,-10.0</em>) 		<em>// 偏移量</em>
	<q>Rect</q>.<em>fromCenter(center: Offset(10.0, 0.0), width:20.0,height: 20.0)</em>
)